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    Influence of polyoxometallates as additive on electro-winning of copper
    (Elsevier Science Bv, 2016) Ehsani, Arman; Yazici, Ersin Y.; Deveci, Haci
    In this paper, the electro-winning of copper from synthetic copper sulphate solutions and the pregnant leach solution (PLS) derived from the leaching of e-waste was investigated in an attempt to reduce energy consumption by using a polyoxometallate (POM), ammonium metatungstate hydrate (AMTH) as a novel additive. Effect of addition of AMTH on the current efficiency, rate of copper deposition, deposit quality and morphology was studied. The current efficiency was determined to be 7% lower in the electro-winning of copper from the pregnant leach solution than that from the synthetic solution (84% vs 91%) presumably due to the presence of impurities (e.g. Fe) in the former. The addition of AMTH (50-100-200 mg/L) into the synthetic electrolyte solution was found to increase the current efficiency (by 3-8%) as well as the rate of copper deposition at the current densities tested (150-250-300 A/m(2)). Effect of AMTH on the surface morphology of copper deposit was also examined. Despite its beneficial effect on the current efficiency and rate of copper deposition, the deposit morphology tends to deteriorate (i.e. rough/dendritic texture) with increasing the concentration of AMTH in both PLS and synthetic copper sulphate solution. It can be inferred from the findings that AMTH can be used as an additive for reducing power consumption in electro-winning of copper from sulphate solutions. (C) 2016 Elsevier B.V. All rights reserved.
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    Recovery of metals from chloride leach solutions of waste of printed circuit boards by adsorption and precipitation
    (Gecamin, 2014) Yazici, Ersin; Deveci, Haci; Ehsani, Arman
    The downstream treatment of chloride leach solutions of WPCB for recovery of base and precious metals by a combination of adsorption and precipitation processes were carried out. A synthetic leach solution (1 M HCl, 116.5 g/L Cl-, 30 g/L Cu2+, 2.5 g/L Fe3+, 5 mg/L Au3+, 10 mg/L Ag+ and 20 mg/L Pd2+), which was prepared based on the composition of the pregnant leach solution obtained in the previous study was used in the tests. The leach solution was initially subjected to activated carbon (AC) adsorption #y(20 g/L AC, 80°C) in which gold was selectively recovered over silver and palladium i.e., 88% Au recovery at 0.5 h (92% at 3.5 h) compared with only 3-6% for Ag/Pd. Copper and iron were also observed to adsorb on AC as indicated by 1.4% and 17% decline, in their respective concentrations. Following the adsorption and filtration stage, metallic copper was added into the gold-barren solution to allow reduction of Cu2+ to Cu+, and to cement Pd on metallic copper. Over the mixing period (1 h), 93% of the Pd was recovered while only 1.4% of silver was cemented onto metallic copper. Subsequently, the leach solution was gradually neutralised by NaOH to pH 4, 7.5 and 9.5 for the precipitation of copper as cuprite (Cu2O). It was found that 41% and 46% of Cu and Ag, respectively, were precipitated at pH 4 at which iron was almost totally (99.8%) removed from solution. Precipitation of copper and silver was increased further at high pHs. At pH 9.5, cumulative recoveries for copper and silver were 91% and 85%, respectively. XRD analysis of the precipitates confirmed the presence of cupric copper oxides/hydroxides and revealed that copper losses occurred at pH 4 was due to the undesired presence of cupric copper in the solution.